The subject matter disclosed herein relates to refrigerator appliances, and more particularly to controlling the flow of a refrigerant in such a refrigerator appliance.
Many existing refrigerator appliances are based on a vapor-compression refrigeration technique. In such a refrigeration technique, a refrigerant serves as the medium that absorbs and removes heat from the space to be cooled, and transfers the heat elsewhere for expulsion. A refrigeration system that performs such a technique typically utilizes some type of refrigerant flow mechanism to control the flow of the refrigerant through the system.
For example, in medium and large sized refrigeration units such as commercial air conditioners and commercial ice makers, a thermal expansion valve is typically used to regulate the flow of the refrigerant. For a household refrigerator, a capillary tube is typically used to regulate the refrigerant flow. This is because the refrigerant flow rate in a household refrigerator is relatively small, as compared to commercial refrigeration units.
However, a capillary tube has a fixed diameter and fixed length, and therefore can only provide a fixed refrigerant flow rate at a fixed pressure. That is, once designed, the refrigerant flow rate of a refrigerator using a capillary tube can not be adjusted without varying the compressor speed. If the operating conditions of the refrigerator diverge from the designed operating condition for which a particular capillary tube has been selected, then the performance and energy consumption of the refrigerator are compromised.
Some refrigerator appliances are designed to have two separate evaporators, for example, one serving as an evaporator in a freezer compartment of the refrigerator (i.e., a freezer evaporator) and the other serving as an evaporator in a fresh food compartment of the refrigerator (i.e., a fresh food evaporator). The evaporator is the part of the refrigeration system through which the refrigerant passes to absorb and remove the heat in the compartment being cooled (e.g., freezer compartment or fresh food compartment).
In such dual evaporator refrigeration systems, a three-way valve has been used to control refrigerant flow. Such a three-way valve has one input port and two output ports, wherein the outputs are respectively coupled to the evaporators. However, there is no ability to control the flow rate into each evaporator with the three-way valve. Rather, only flow direction can be controlled by turning the refrigerant flow on or off for each of the evaporators, i.e., by fully opening and fully closing the output ports of the three-way valve.